If you find mistakes, I will be thankful for telling me
After teaching them a few spells, Dezen let undead train them, and while they did so, he was observing them to check if there will be any problems.
At some point of feeling his mana being used, he got curious how it looks in his soul. Thus, he focused on it (his soul), like he always does before cultivating, and then started observing how different colours flow and mix with each other.
In his soul, there were tens of tiny spots, where his necromancy mana was constantly going. Dezen discorvered them soon after he started cultivating, and called them "marks". He believes that they are the things, thanks to which he can fell his connection with his undead. Besides this, Dezen can also include them in his spells, what he did while creating the one to control his undead.
3 of these marks were getting more of that green mana than the others. Sometimes they were also getting other kinds of mana, like earth or space. Of course, these 3 marks belonged to his human undead, and as it turned out, normal humans also can use spells, after they become undead. Therefore, he decided that it will be better to get only corpses of normal humans and great mages, that could possess unknown spells and valuable knowledge.
After observing the flow of the mana and thinking how his future will look like, if he uses fact correctly, Dezen realized something.
"Stronger mages should have some hideouts, and treasures in there. If I get them... " - He started imagining what he could gain, before coming back to being down to earth - " By the time I am strong enough to kill them myself, or to buy their corpses, it won't so valuable for me. And the Church probably won't kill them so I can turn them into undead..." - His next thoughts were more of a images than words. - " However, they may ask me to turn them into undead, if capturing wasn't possible, and they had to be killed... No, the chance is too small. I shouldn't hope for it."
***
During the next days, the progress of creating the spell to see memories of his undead was slow, too slow to it continuing had any sense. Instead, Dezen decided to get mind magic, which, besides making the process faster, it will be useful in the future.
After making the decision, he headed to the church, from where he get to one of the Church of Alen's fortresses. There Dezen could find assignments that he would like to fulfil, and this way earn for the mind magic.
Not long after, Dezen found assignment, that he was fond of. Due to the Replacements of the terrain, and appearances of unknown creatures, Church wanted to make maps presenting which areas are safe, where unknown creatures may be came across, and which surely have them and/or are alien landscapes.
Thanks to his undead, Dezen could explore these areas safely, without any fear of getting harmed, unless something he encounters has ability to feel the connection between him and his undead, and use it to attack him. Even his undead won't be affected, because to get rid of them, their whole bodies have to be destroyed, and he can just seperate part of them, from which they will regenerate, in the safety of his home.
To get better effects, Dezen decided to get more undead. He also used this opportunity to test his new fight strategy, where he will be using senses of the undead, but without controlling. Instead, he will be casting spells through them, while the undead move on their own.
***
To get new undead, Dezen sent one of his wolves with humanoid shape to the forest, on which he casted spell making him faster. He wasn't overseeing him the whole time, since he had to start cultivating madly, to keep his mana production satisfyingly high. Dezen only did at the begging, when the undead was leaving the barrier.
From observing the forest for only a few seconds, Dezen could tell something changed. He wasn't entirely sure what it was, but it surely got more dangerous. Dezen could tell not only by his fellings, but also thanks to common knowledge. It is widely known in this world, that if not the Gods protecting people, they would be wiped out by animals, and part of that protection were spells, making dangerous creatures too terrified to get close to any human habitats. However, now they stopped working, since the villages got barriers and mages to guard them, and the creatures dare to approach.
For Dezen it were good news, since he would meet these animals faster.
Dezen stopped observing after a few minutes, and came back to cultivating. The wolf have ability to contact with Dezen, and was said to do so when he will be fighting with something, or when he finds dead creatures. Thus, he only had to wait, for what soon happened.
What the undead found was heavily decomposed corpse, which is unable to recognise too what creature it belonged. Dezen looked at it for a few seconds, and then lost all of his interest. He was also commenting it in his thoughts, and for some unknown to him reason, he called it "dead matter".
"Dead matter.... Dead matter? Like most of the things this world is made from, like rocks, metals, water, air. Well, necromancy lets me turn what was once alive and died into undead, but if I could turn what was always dead into undead. " - He started imagining what he could achieve, what was images and scenes, not words. - "I could also make a spell that will seek for dead creatures. Would be useful, but it is not really needed now."
Curious if the spell creating undead would work on anything else than corpses, he casted it on the rocks nearby the wolf, and the soil it was standing on.
The undead was just standing there, observing as the green fire appears, but does nothing. It was what Dezen expected, so he left the wolf, focusing on creating a new spell.
Few hours later, the wolf contacted him once again. During this exploration, he meet other animals, but he didn't inform Dezen about it. It was because he was told to do so, only when they attack him. That means, they aren't afraid of the undead, and are fast enough to get him.
To create the map wanted by the Churh of Alen, his undead would need to explore really dangerous areas, that belong to humanity only in theory. Thus, his undead have to be strong. However, finding powerful creatures is hard, since they are rare, so he has to be satisfied with fast ones.
What attacked the undead wolf was small drove of brown birds. They resemble eagles, with main difference being their heads, round, almost like perfect balls with long, thin beaks.
After glancing at them for less than a second, Dezen casted 2 spells to protect the wolf, one made invisible barrier around his body and the second one set his whole body on fire, which burns anything that wamts to touch him. At the same time, undead was moving, trying to dodge the birds and hurt them with his claws.
To attack these birds, called vankers, Dezen was mostly using telekinesis, crushing their wings. Sometimes, he was also setting them on fire, by creating flames on their bodies.
Around 7 seconds passed, and the birds who could backed off. The rest was killed, and quickly turned into undead by Dezen. Then, he looked at vankers, thinking what to do next. The birds already lost 7 of them, and started fleeing, knowing they won't kill the wolf. Dezen tried to shoot them down, but they perfectly dodged every spell. There were also 2 vankers left, who were still burning and couldn't fly. He turned his gaze toward them, and ended their suffering with telekinesis.
After turning these 2 into undead, Dezen ordered all of these birds to go to his home, where he will cut off parts of their bodies. He also wanted to examine them, and keep at least 1 with him.
Since the fight occurred relatively closely to the village, Dezen didn't have to wait too long. With the help of one of his human undead, he started examinations. At first they were cutting through their insides, comparing them between different undead, before focusing on their muscles, bones and so on. During the process, they cut off many parts of their bodies, which Dezen then stored.
Dezen was also interested in the abilities vankers have. From informations he bought, he knew that they are magical creatures, but their magic is not meant for humans. That means, humans cannot learn it or absorb its mana.
From a few tests he made, Dezen found out that this magic focuses on making their bodies and reactions faster. There was also interesting ability, that changes trajectory of spell shoot at them, helping them while dodging.